Electric power lines are held in their overhead position using support structures. The support structures typically include horizontal cross members or cross arms which are braced to, typically vertical, poles. The vertical poles may be made of wood, steel or concrete. To avoid downtime, maintenance and repair work may be carried out to the power lines and/or support structures when the power lines are energized.
Maintenance or repair work to the poles may include replacing old poles with new poles. Of course, new pole installations are also often needed. In both instances, the new pole being installed must be set in a base, such as in the ground. Since most pole installation work is done in the vicinity of energized power lines, there are safety concerns when an operator is installing new poles in such a setting. Safety concerns are heightened when the power lines carry voltages in the transmission-class (69 kV to over 500 kV).
Typically setting a pole involves the following procedure: a worker, standing on the ground, attaches a chain, cable or other tether to a new pole lying on the ground, and an operator operates a hoist or crane to lift the pole using the tether so as to suspend the pole above the ground, hopefully more or less vertically. The operator positions the lower end or butt of the pole over a hole which has been dug in the ground in the desired location of the pole. One or more workers, standing on the ground, manipulate the lower end of the pole as it is being set in the hole. New poles, during their setting, are not connected to energized transmission lines but are still inherently at least partially conductive due to induced electric fields generated by the energized transmission lines in the vicinity. The poles become more conductive if they are wet or dirty. In order to protect operators from touching the new poles being set and thus subjecting themselves to possibly injurious or fatal electric currents, the United States federal Occupational Safety and Health Administration (OSHA) has ruled that when a pole is set, moved, or removed near an exposed energized overhead conductor, the employer shall ensure that each employee wears electrical protective equipment or uses insulated devices when handling the pole and that no employee contacts the pole with uninsulated parts of his or her body.
For distribution-class voltages (typically 750 V to 34 kV), during setting, a worker on the ground is in close proximity to the pole. The lower end of the pole is typically manipulated by one or more workers wearing insulated rubber gloves. For transmission-class voltages, applicant is aware that in some instances one or more ropes are attached to the lower end of the pole and the pole is manipulated by one or more workers each holding the free end of one of the ropes at a distance from the pole.
However, continually reducing the possibility of accidents is desirable. One example of a potential accident is an operator who may lose control of a new pole being set, for example by having the tether attached too close to the pole's center-of-gravity so that the pole doesn't lift to the vertical but may teeter about the horizontal, risking contact with power lines, etc. when the pole is lifted to be set. In another example, upon lifting the pole, the end of the pole still in contact with the ground may simply roll, thus causing the entire pole to slightly change position while being held by the tether. In the event that the pole in either pole-setting situation, or another situation, accidentally contacts an energized electrical transmission line, the pole itself may then become energized. For transmission-class voltages, this may be particularly hazardous as the voltage or electrical potential may be sufficient to burn the rope (if rope is being used to manipulate the lower end of the pole) and may cause harm to the workers manipulating the pole. Even if the workers wear insulated rubber gloves while holding the free end of the rope, the gloves would likely not adequately insulate a person and provide protection from transmission class voltage levels.
Applicant is not aware of any physically and electrically isolating device that will provide workers on the ground with secure and positive control of the lower end of a new pole during the setting of the pole, for example where the pole is a transmission-class pole to support transmission class electrical conductors. While live line tools such as insulated grip-all clamp sticks for isolating workers from certain voltage classes do exist, improvement is desired.
Thus, there is a need for a device and method which would not only maintain a physical working distance between a worker on the ground, hereinafter also referred to as a “ground worker”, and a potentially electrically conductive pole, but which would also electrically isolate the ground worker from the potentially conductive pole should it accidentally become energized.